This application in general relates to a valve arrangement for a regenerative incinerator.
Incinerators are known in the prior art which include a plurality of regeneration heat exchange chambers leading into a combustion chamber. The heat exchange chambers each move cyclically through inlet, purge and outlet modes. In an inlet mode cool air to be cleaned, containing impurities such as paint solvents, is lead into a combustion chamber through one of the heat exchange chambers. This air to be cleaned will be referred to as "dirty" air for the purposes of this application. As air is entering the combustion chamber through one heat exchange chamber, a second heat exchange chamber in an outlet mode is receiving hot clean air which had previously been combusted in the combustion chamber. The cool and hot air passes cyclically through the heat exchange chambers, alternatively heating and cooling them. In this way, the cool air leading into the combustion chamber is preheated, increasing thermal efficiency.
This type of incinerator operates continuously with at least one chamber in an inlet mode sending preheated air into the combustion chamber, and at least one chamber in an outlet mode receiving hot air from the combustion chamber. In this way relatively large volumes of air are cleaned.
More recently, the use of a purge mode has been used after the inlet mode, and before the beginning of the outlet mode. The purge mode ensures that any dirty air left in the heat exchange chamber from the previous inlet mode will be removed before the outlet mode begins. If dirty air remained in the heat exchange chamber, that air could move with the outlet air into a downstream destination, such as atmosphere, reducing combustion efficiency.
The prior art incinerators typically have at least three heat exchange chambers. There are valves for each of the three modes leading into and out of each heat exchange chamber. Thus, there are at least nine valves, and valve control becomes relatively complicated.
Typically, the prior art has used electronic or hydraulic controls to actuate valves. Such systems may be less efficient than desired. It is somewhat difficult to properly time the opening and closing of the valves associated with each of the several heat exchange chambers and maintain steady inlet pressures. It is important to insure that no dirty air reaches the outlet for optimum combustion efficiency. For this reason when a purge cycle is used the timing of each mode of operation, during each cycle, for each chamber, is critical. Further, hydraulically opened and closed valves tend to restrict the flow of the fluid through the valves severely once they begin to close, but then taper slowly to zero. Due to this, the valves are restricted resulting in low flow percentages for a relatively long portion of the cycle. They are somewhat slow to respond, and result in flow peaks rather than smooth operation. Each of these problems is undesirable.
Further, the prior art systems have typically ended an inlet cycle and then had a pause or delay before beginning the purge or outlet cycles. This results in overly long cycling time, and reduced volume flows for a given time period.
Various types of cams and other mechanical actuation systems have been used to open and close inlet and outlet valves in this type of regenerative incinerator. Further, mechanically operated means which have utilized eccentrically mounted secondary shafts driven by a main shaft have been used to actuate inlet and outlet valves. Mechanically operated means have not been used to open and close valves associated with the inlet, outlet, and purge lines. As discussed above, the timing of the purge mode is critical.
Further, the prior art systems have typically segregated the modes between inlet, outlet and purge cycles. These systems have waited until the inlet valve is completely closed before beginning the purge mode. Also, they have waited till the purge mode ended before beginning the outlet mode. With the use of the prior art hydraulically actuated valves this may take a relatively long period of time increasing the cycle time and reducing the flow volume for a given period of time.